Electrically conductive, preferably unbacked adhesive tape with permanent full-area pressure sensitive adhesion, composed of a film of a pressure sensitive adhesive which is preferably coated onto an antiadhesive medium and has an alkaline surface

ABSTRACT

A preferably unbacked adhesive tape with permanent full-area pressure sensitive adhesion, composed of a film of a pressure sensitive adhesive which is preferably coated onto an antiadhesive medium and comprises  
     an alkaline, solid, pulverized, mineral filler with a weight fraction of between more than 5% by weight and 60% by weight, based on the total weight of the adhesive, so that the permanently pressure sensitively adhesive surface of the adhesive tape has a pH of more than 8, and  
     a conductive additive, especially a metal powder, a powder coated with a metal, and/or metallized beads, with a weight fraction of between more than 5% by weight and 60% by weight, so that the adhesive tape is electrically conductive in the z direction, i.e., in the direction of the thickness of the tape.

[0001] The invention relates to an adhesive tape which is permanentlypressure-sensitively adhesive over the entire surface, is preferablyunbacked, and is composed of a film of a pressure sensitive adhesivewhich is preferably coated onto an antiadhesive medium.

[0002] Electrostatic filters in air conditioning units have theadvantage over conventional mechanical filters (fabrics, paper, etc.) ofa substantially reduced pressure drop, low energy costs, and less noise.Nevertheless, like the conventional filters, they too offer a nutrientmedium for microorganisms, as a result of the deposited dust. Themicroorganisms multiply on the electrode surfaces, and finally there isdetachment. The microorganisms are taken up by the flow of air andbecome dispersed in the interior air.

[0003] Regarding the denaturing of microorganisms in electrostaticfilters there have been a series of proposed solutions. DE 198 22 055A1, for example, specifies a denaturing electrode composed of individualdenaturing layers differing in electrical resistance and in pH.

[0004] DE 198 22 054 A1 describes an electrostatic filter separationsystem with a denaturing neutralization chamber.

[0005] DE 299 10 747 U discloses the use of highly alkaline or acidicfilter mats to solve the problem.

[0006] A porous plastic coating removable by washing and comprising adenaturizing salt, mounted on the surface of the filter, is proposed asa solution to the problem by DE 198 07 295 A1.

[0007] Although the abovementioned proposals solve the problem of themultiplication of microorganisms in electrostatic filters and theirsubsequent dispersion in the interior air, they have the disadvantage oflacking sufficient efficacy and of not being sufficiently costeffective. The systems are complicated and cannot be used withsufficient universality.

[0008] DE 199 12 628 A1 describes an electrically conductive adhesivesheet which is thermoplastic and heat-activatable and has the followingcomposition:

[0009] i) a thermoplastic polymer with a fraction of from 30 to 89.9% byweight,

[0010] ii) one or more tackifying resins with a fraction of from 5 to50% by weight and/or

[0011] iii) epoxy resins with hardeners, and possibly accelerators aswell, with a fraction of from 5 to 40% by weight,

[0012] iv) silverized glass beads or silver particles with a fraction of0.1% by weight, with very particular preference 10% by weight, to 40% byweight.

[0013] The adhesive sheet is a mixture of reactive resins whichcrosslink at room temperature and form a three-dimensional polymernetwork of high strength, and of permanently elastic elastomers, whichcounter any embrittlement of the product.

[0014] The particularly preferred thermoplastic polyurethanes (TPUs) areknown as reaction products of polyester polyols or polyether polyols andorganic diisocyanates such as diphenylmethane diisocyanate. They arecomposed of predominantly linear macromolecules. Such products aremostly available commercially in the form of elastic granules: forexample, from Bayer AG under the trade name “Desmocoll”.

[0015] The silver particles may be composed of pure silver but may alsobe manufactured as an alloy, which in that case should include aconsiderable fraction of silver in order to ensure conductivity.

[0016] The electrically conductive, thermoplastic, and heat-activatableadhesive sheet serves for the permanent bonding of two articles. Incontradistinction to bonds with a pressure sensitive adhesive tape,strengths such as those required in the construction sector are achievedlong-term here and are retained even under burdensome chemical, thermalor climatic conditions.

[0017] Following appropriate converting, punched portions or rolls ofthis adhesive sheet can be adhered at room temperature or at slightlyelevated temperature to the substrate that is to be bonded (electroniccomponent, module, etc.).

[0018] The admixed reactive resins should not undergo any chemicalreaction at the slightly elevated temperature. Thus the bonding must notoccur as a single-stage process; instead, for the sake of simplicity, asin the case of a pressure sensitive adhesive tape, the adhesive sheetcan be attached first to one of the two substrates by thermallamination. During the actual hot adhesive bonding process with thesecond substrate, the resin then cures partly or wholly and the jointachieves the high bond strength, far above that of pressure sensitiveadhesive systems.

[0019] Accordingly, the adhesive sheet is particularly suitable for hotpressing at temperatures below 120° C., in particular from 80° C. to100° C.

[0020] The use of metallic or metallized materials for achievingelectrical conductivity in adhesive films is further described in EP 0734 576 A1.

[0021] Neither the adhesive sheet nor the adhesive film, however,exhibit any properties which suggest their use against microorganisms.

[0022] DE 196 14 620 A1 discloses a pressure sensitive self-adhesivetape, coated on both sides with adhesives, whose backing is formed by aformulated, crosslinked, unfoamed polyurethane.

[0023] One constituent used for the backing is a crosslinked, unfoamedpolyurethane which is formulated with additional components, namelyfillers, plasticizers and resins, and also, where appropriate, furtherauxiliaries.

[0024] The polyurethane content of the backing is up to 50% by weight,preferably from 10% by weight to 40% by weight. The fillers make up from40% by weight to 70% by weight of the backing, while the plasticizersand resins are used together at from 5% by weight to 30% by weight, inparticular from 10% by weight to 25% by weight.

[0025] The selection of the isocyanate component of the polyurethane isgoverned by the specific properties to be established in the backing.Suitable examples include tolylene diisocyanate, diphenylmethane4,4′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, hexamethylenediisocyanate, isophorone diisocyanate, mixtures of said isocyanates orisocyanates derived chemically from them, dimerized or trimerized types,for example.

[0026] The selection of the isocyanate-reactive component is likewisegoverned by the properties of the backing that are to be established asa function of the desired profile of requirements. Suitable examplesinclude all polyesterdiols, -triols, and -polyols, polyetherdiols,-triols and -polyols.

[0027] In one particularly preferred embodiment of the self-adhesivetape the polyurethane is formed using a hydroxyl-functionalizedpolybutadiene in conjunction with a diisocyanate.

[0028] Fillers which can be used include both reinforcing fillers, suchas carbon black, for example, and nonreinforcing fillers, such as chalkor barium sulfate, for example. Further examples are talc, mica, silica,silicates or zinc oxide. Mixtures of said substances may also be used.

[0029] Examples of plasticizers are phthalates and paraffinic,naphthenic or aromatic mineral oils. Resins which can be used includephenolic resins, hydrocarbon resins or bitumen.

[0030] Adhesives which can be used include rubber-based oracrylate-based adhesives of which there was general prior knowledge.

[0031] DE 197 33 014 A1 likewise discloses a pressure sensitive,double-sided self-adhesive tape comprising a backing coated on bothsides with pressure sensitive adhesives and composed

[0032] a) in a weight fraction of up to 50% by weight, in particularfrom 30% by weight to 40% by weight, of a crosslinked, unfoamedpolyurethane,

[0033] i) formed from hydroxyl-functionalized polybutadiene,polyesterdiol, polyestertriol, polyesterpolyol, polyetherdiol,polyethertriol or polyetherpolyol, polyetherdiamine, polyethertriamine,polyetherpolyamine and also monohydric alcohol (monool), monofunctionalamine (monoamine), polyethermonool, polyethermonoamine, or of productsderived from the four last-mentioned groups

[0034] ii) and of diisocyanate or chemically derived isocyanate,

[0035] iii) the polyurethane being plasticizer-free,

[0036] b) in a weight fraction of from 50% by weight to 70% by weight offillers,

[0037] c) if desired, of further auxiliaries.

[0038] This adhesive tape differs from that of DE 196 14 620 A1 in thatit is plasticizer-free.

[0039] The self-adhesive tapes disclosed here, consisting essentially ofa laminate comprising a formulated polyurethane composition and apressure sensitive adhesive film necessarily have a three-layerconstruction: adhesive film/formulated polyurethane composition/adhesivefilm.

[0040] It is an object of the invention to develop a preferablyunbacked, double-sided adhesive tape for attachment to the electrodes ofelectrostatic filters in air conditioning units which in order to ensurethe electrical functionality of the electrostatic filters iselectrically conductive in the z direction and at the same timepossesses a surface which both has permanent inherent adhesiveness orpressure-sensitive adhesiveness and is permanently alkaline, so thatmicroorganisms can be picked up from the stream of air and cured orhindered in their further multiplication. Moreover, it ought to bepossible to wash the surface of the adhesive tape with mains water sothat following dust accumulation or other soiling occurring unavoidablyover the course of time, the original pressure sensitive adhesivenesscan be reestablished.

[0041] This object is achieved by means of an unbacked adhesive tape asspecified in the main claim. The subclaims embrace advantageousembodiments thereof and also one particularly appropriate application.

[0042] The invention accordingly provides a preferably unbacked adhesivetape with permanent full-area pressure sensitive adhesion, composed of afilm of a pressure sensitive adhesive which is preferably coated onto anantiadhesive medium and comprises

[0043] an alkaline, solid, pulverized, mineral filler with a weightfraction of between more than 0% by weight and 60% by weight, based onthe total weight of the adhesive, so that the permanently pressuresensitively adhesive surface of the adhesive tape has a pH of more than8, and

[0044] a conductive additive, especially a metal powder, a powder coatedwith a metal, and/or metallized beads, with a weight fraction of betweenmore than 0% by weight and 60% by weight, so that the adhesive tape iselectrically conductive in the z direction, i.e., in the direction ofthe thickness of the tape.

[0045] In one first advantageous embodiment of the adhesive tape theparticle diameter of the mineral filler, based on at least 80% of saidparticles, is not more than 0.5 mm, preferably not more than 0.1 mm.

[0046] In another advantageous embodiment of the adhesive tape theparticle diameter of the conductive additive, based on at least 80% ofsaid particles, is at least 30% of the thickness of the pressuresensitive adhesive film, preferably at least 70% of the thickness ofsaid film.

[0047] It is further advantageous if the weight fraction of the mineralfiller is from 5% by weight to 40% by weight, preferably from 5% byweight to 30% by weight, with very particular preference from 5% byweight to 20% by weight, based on the total weight of the pressuresensitive adhesive.

[0048] It is further advantageous if the weight fraction of theconductive additive is from 10% by weight to 30% by weight, based on thetotal weight of the pressure sensitive adhesive.

[0049] Suitable base polymers for the pressure sensitive adhesive of thepreferably unbacked adhesive tape include all elastomers customary inthe formulation of pressure sensitive adhesives.

[0050] Preferred elastomers are copolymers based on acrylic acid,methacrylic acid and their esters, maleic, fumaric, and itaconic acidand their esters, substituted (meth)acrylamides, other vinyl compounds,such as vinyl esters, vinyl acetate, vinyl alcohol and/or the estersthereof, for example, natural rubber, styrene block copolymers,polybutadiene, polyisoprene, polychloroprene rubber, butyl rubber,silicone rubber, EPDM rubber, ethylene-propylene copolymers,polyurethanes, vinyl copolymers, ethylene-vinyl acetate copolymers,vinyl chloride-acrylate copolymers, polyether esters, polyether amidesand polyester amides, polycarbonate-polyester copolymers,ethylene-acrylate copolymers, and ABS copolymers.

[0051] The aforementioned elastomers may also be used as a constituentin polymer blends.

[0052] The base polymers may be compounded appropriately with resins orother blending components, such as fillers, plasticizers, pigments,stabilizers, catalysts, aging inhibitors, light stabilizers or UVstabilizers, for example.

[0053] Fillers which can be used include both reinforcing fillers, suchas carbon black, and nonreinforcing fillers, such as chalk, bariumsulphate or zinc oxide, for example.

[0054] The function of the light stabilizers is primarily to preventembrittlement of the adhesive tape. Light stabilizers of this kind aredescribed in Gaechter and Muller, Taschenbuch der Kunststoff-Additive,Munich 1979, in Kirk-Othmer (3rd) 23, 615-627, in Encycl. Polym. Sci.Technol. 14, 125-148, and in Ullmann (4th) 8, 21; 15, 529, 676. HALSstabilizers in particular are suitable for the adhesive tape of theinvention. The amount of light stablizer should be at least 0.15% byweight, preferably at least 0.30% by weight, based on the pressuresensitive adhesive.

[0055] The use of antioxidants is advantageous but not mandatory.Further suitable UV absorbers, light stabilizers, and aging inhibitorsare listed in EP 0 763 584 A1, which is hereby incorporated by referenceto become part of this disclosure.

[0056] In one particularly preferred embodiment, the base polymer of thepressure sensitive adhesive of the preferably unbacked adhesive tape ispolyurethane.

[0057] The polyurethane-based pressure sensitive adhesive can beprepared using both aliphatic and aromatic isocyanates.

[0058] Suitable examples include isophorone diisocyanate, hexamethylenediisocyanate, dicyclohexylmethane 4,4′-diisocyanate, tolylenediisocyanate, diphenylmethane 4,4′-diisocyanate or m-tetramethylxylenediisocyanate, mixtures of said isocyanates or isocyanates derivedchemically therefrom, dimerized, trimerized or polymerized types forexample, containing for example urea groups, uretdione groups orisocyanurate groups.

[0059] As the isocyanate component it is also possible, furthermore, touse prepolymers, in other words reaction products of isocyanate andpolyol prepared beforehand in an NCO/OH ratio of more than one.

[0060] In one preferred embodiment the polyol component used comprisespolypropylene glycols, polyethylene glycols, hydrogenated,hydroxyl-functionalized polyisoprenes, hydroxyl-functionalizedpolyisobutylenes or hydroxyl-functionalized polyolefins. Also suitableare hydroxyl-functionalized polybutadienes and other, hydrogenated andnonhydrogenated, hydroxyl-functionalized hydrocarbons.Polytetramethylene glycol ethers (polytetrahydrofurans) are likewisesuitable. Suitability extends to polyesterpolyols and also mixtures ofthe aforementioned polyol components. As the polyol component it islikewise possible to use reaction products of isocyanate and polyolprepared beforehand in an NCO/OH ratio of less than 1. Known chainextenders, short-chain crosslinkers or terminators may likewise be usedin forming the polyurethane layer.

[0061] In order to achieve an appropriate coating viscosity, thepolyurethane components may also be diluted with solvents.

[0062] Besides the isocyanate components listed and the polyolcomponents which react with them, other starting materials may also beused for forming the polyurethane without departing from the concept ofthe invention. In particular, amine-functionalized components, such aspolyether amines or amino-containing chain extenders or crosslinkers,for example, may be employed in preparing the polyurethane-basedpressure sensitive adhesive.

[0063] In order to accelerate the reaction between the isocyanatecomponent and the isocyanate-reactive component, it is possible to useany catalysts known to the skilled worker, such as tertiary amines,organobismuth compounds or organotin compounds, for example,

[0064] Polyurethanes as above are prior art in terms of theirpreparation and are described, for example, in “Ullmann's Encyclopediaof Industrial Chemistry”, Vol. A21: Polyurethanes.

[0065] In one possible embodiment the polyurethane-based pressuresensitive adhesive comprises other formulating ingredients, such asfillers, pigments, rheological additives, plasticizers, resins(tackifiers), elastomers, aging inhibitors (antioxidants), lightstabilizers, UV absorbers, and other auxiliaries and additives, such asdriers (for example, molecular sieve zeolites, calcium oxide), flowcontrol agents and leveling agents, wetting agents (surfactants) orcatalysts, for example.

[0066] Fillers which can be used include all finely ground solidadditives such as, for example, chalk, magnesium carbonate, zinccarbonate, kaolin, barium sulfate or titanium dioxide. Further examplesare talc, mica, silica, silicates or zinc oxide. Mixtures of saidsubstances can also be used.

[0067] The pigments used may be organic or inorganic in nature. Examplesare all types of organic or inorganic color pigments, especially whitepigments such as titanium dioxide, for instance.

[0068] Examples of rheological additives are pyrogenic silicas,phyllosilicates (bentonites), high molecular mass polyamide powders orcastor oil derivative powders.

[0069] Examples of plasticizers are phthalates, trimellitates,phosphates, esters of adipic acid, and other acyclic dicarboxylateesters, fatty acid esters, hydroxycarboxylic esters, alkylsulfonicesters of phenol, aliphatic, cycloaliphatic, and aromatic mineral oils,hydrocarbons, liquid or semisolid rubbers (for example, nitrile rubbersor polyisoprene rubbers), liquid or semisolid polymers of butene and/orisobutene, acrylates, polyvinyl ethers, liquid resins and soft resinsbased on the raw materials which are also the basis for tackifierresins, wool wax and other waxes, silicones, and polymer plasticizerssuch as polyesters or polyurethanes. Particularly suitable plasticizersare aging-stable plasticizers without an olefinic double bond.

[0070] Suitable resins (tackifiers) are all natural and syntheticresins, such as rosin derivatives (for example, derivatives formed bydisproportionation, hydrogenation or esterification), coumarone-indeneresins and polyterpene resins, aliphatic or aromatic hydrocarbon resins(C-5, C-9, (C-5)₂ resins), mixed C-5/C-9 resins, hydrogenated andpartially hydrogenated derivatives of said types, resins of styrene orα-methyl styrene, and also terpene-phenolic resins and others as listedin Ullmann's Enzyklopadie der technischen Chemie, Volume 12, pp. 525 to555 (4th ed.), Weinheim.

[0071] The particularly preferred base polymer of the polyurethanepressure sensitive adhesive may be blended with suitable elastomers,such as are listed individually above, in polymer blends.

[0072] It is particularly preferred if more than 50% by weight of thepolymer basis of the pressure sensitive adhesive comprises polyurethane.

[0073] The use of antioxidants, such as sterically hindered phenols(Irganox 1010 or trisnonylphenyl phosphite) is advantageous in thepolyurethane-based pressure sensitive adhesive as well, although notmandatory.

[0074] Light stabilizers and UV absorbers can also be used, but are notneeded.

[0075] Light stabilizers used likewise include those disclosed inGaechter and Muller, Taschenbuch der Kunststoff-Additive, Munich 1979,in Kirk-Othmer (3rd) 23, 615-627, in Encycl. Polym. Sci. Technol.14,125-148, and in Ullmann (4th) 8, 21; 15, 529, 676.

[0076] Formulating the polyurethanes with further ingredients, such asfillers and plasticizers, for example, is employed in particular whenpreparing sealants (cf. Ullmann's Encyclopedia of Industrial Chemistry,Vol. A 23: Sealing Materials).

[0077] An exemplary listing of documents giving information onformulating and preparing polyurethane-based pressure sensitiveadhesives comprises U.S. Pat. No. 3,930,102 A1, AU 86 53399 A1, JP 59105 069 A1, U.S. Pat. No. 829,691 Al, DE 24 35 218 A1, DE 21 39 640 A1,DE 19 41 022 A1, EP 0 305 175 A1, EP 0 882 749 A1 and U.S. Pat. No.3,761,307 A1.

[0078] In a further preferred embodiment, the polyurethane is formedwith an NCO/OH ratio of from 0.6 to 1.2.

[0079] Moreover, the polyurethane-based pressure sensitive adhesive mayalso have been foamed. Both chemical and physical foaming techniques arepossible.

[0080] As an alkaline filler, all minerals whose pH on wetting withwater is more than 8 are suitable. Examples are metal oxides, especiallyalkali metal and alkaline earth metal oxides, metal hydroxides,especially alkali metal and alkaline earth metal hydroxides, carbonates,phosphates, and cyanides, especially those in each case of the alkalimetals and alkaline earth metals, and also mixtures of these fillers ormixtures of these and other fillers.

[0081] Suitable metal powders include in particular copper, silver,gold, aluminum, nickel, chromium, iron or alloys or mixtures thereof.Metallized powders or beads include all mineral or glass-based orplastic-based powders or beads, respectively, which have been coated inwhole or in part with a metal.

[0082] A coarse mesh or weave may have been let into the pressuresensitive adhesive film, or similar sheetlike structures such asperforated polymer films.

[0083] It is important that the bodies let into the pressure sensitiveadhesive film do not restrict the functional capacity of the adhesivetape of the invention, and especially not the conductivity.

[0084] In order to establish the desired pressure sensitive adhesionproperties, the pressure sensitive adhesive may be chemically orphysically crosslinked. Radiation crosslinking (by EBC or UV, forexample) is likewise possible.

[0085] The pressure sensitive adhesion exists permanently over theentire surface of the adhesive tape. Even prolonged storage periods ofup to one year do not lead to any detractions in terms of pressuresensitive adhesion.

[0086] At the same time, depending on the nature and concentration ofthe alkaline filler, pH values of between 8.5 and 12 are measured withmoistened pH paper. It is preferable if the pH of the pressure sensitiveadhesive surface, especially when moistened, is at least 8.5 or more.

[0087] The volume resistance in the z direction, depending on the natureand concentration of the metal powder, is from 0.05 to 500 Ωm. It ispreferred for the volume resistance of the pressure sensitive adhesivefilm in the z direction to be not more than 500 Ωm, and furtherpreferred if the volume resistance of the polyurethane-based pressuresensitive adhesive film in the z direction is not more than 1 000 Ωm.

[0088] Where the pressure sensitive adhesive film takes on any amount ofdust, road dirt, earth, sand, fat, oil or other substances which reducethe pressure sensitive adhesion, it can easily be cleaned again usingnormal mains water, so that afterward the full, original pressuresensitive adhesion is reestablished and the adhesive tape, especiallywith the polyurethane-based pressure sensitive adhesive film, can beused again without restriction.

[0089] It is further advantageous if the bond strength of the pressuresensitive adhesive film is at least 0.1 N/cm; in the case of thepolyurethane-based pressure sensitive adhesive film it is advantageousif said bond strength is with particular preference at least 0.01 N/cm.

[0090] In the rolling ball tack test, at least a figure of 100 mm orless is achieved; with particular preference, in the case of thepolyurethane-based pressure sensitive adhesive film, at least a figureof 300 mm or less.

[0091] The combination of properties represented by pressure sensitiveadhesion, alkalinity, washability, and electrical conductivity in the zdirection advantageously exists uninterrupted over the entire surfacearea of the adhesive tape and not just in segments or sections.

[0092] The coating of the pressure sensitive adhesive onto ananti-adhesive medium, like the compounding of the pressure sensitiveadhesive, may take place from a solution or a dispersion. Alternatively,a solvent-free process is possible in which, for example, for thepurpose of coating, the pressure sensitive adhesive is melted(extrusion, calender or roll process) or in which it is only preparedimmediately prior to coating by the mixing of two or more chemicallyreactive components and thus comes about chemically only during thecoating phase (multicomponent reactive process).

[0093] Reference may be made to a detailed depiction of the state ofknowledge regarding the topic of pressure sensitive adhesives in the“Handbook of Pressure Sensitive Adhesive Technology”, Third Edition, byDonatas Satas (Satas & Associates, 1999).

[0094] A suitable antiadhesive medium comprises all films or papers fromwhich, following application, the pressure sensitive adhesive can beremoved again without destruction or damage; in other words, forexample, films or papers which owing to their material properties arealready sufficiently antiadhesive or which have been provided with anantiadhesive coating such as silicone, polytetrafluoroethylene orpolyethylene, for instance.

[0095] The antiadhesive medium coated with the pressure sensitiveadhesive is preferably wound into a roll. For better protection, thepressure sensitive adhesive may also be lined from the exposed side witha second antiadhesive medium, which need not be identical with thefirst.

[0096] Surprisingly and unforeseeably for the skilled worker, anunbacked pressure sensitive adhesive film which comprises an alkaline,solid, pulverized, mineral filler whose particle diameter, based on atleast 80% of these particles, is not more than 0.5 mm, with a weightfraction of between more than 0% by weight and 60% by weight, based onthe total weight of the pressure sensitive adhesive, and furthercomprising, with a weight fraction of between greater than 0% by weightand 60% by weight, a conductive additive such as a metal powder, ametal-coated powder of any other kind and/or metallized beads (forexample, metallized glass beads) whose particle diameter, based on atleast 80% of these particles, is at least 30% of the thickness of thepressure sensitive adhesive film proves outstandingly suitable forachieving the set objectives, particularly in view of the inventivecombination of the properties of electrical conductivity in the zdirection with both permanent inherent adhesion and permanent pressuresensitive adhesion and the permanently alkaline surface in the adhesivetape of the invention.

[0097] Moreover, especially when it has a polyurethane-based pressuresensitive adhesive film, the adhesive tape of the invention can becleaned with normal mains water when contaminated with dust or otherwisesoiled, and afterward can be used again to its full extent.

[0098] On the basis of the combination of electrical conductivity,permanent pressure sensitive adhesion, and alkalinity, an adhesive tapeof this kind is suitable for application to collecting electrodes ofelectrostatic filters in air conditioning units.

[0099] The tape ensures the basic electrical function of theelectrofilter, picks up microorganisms (bacteria, viruses, fungi, etc.)from the flow of air, prevents their further multiplication or bringsabout their denaturization, and is regenerable by cleaning with mainswater following dust contamination or any other soiling; that is, theoriginal pressure sensitive adhesion, in combination with the surfacealkalinity, can be reestablished.

[0100] For application in service, the adhesive tape is adhered directlyto the substrate and then the antiadhesive medium is peeled off. Astabilizing backing, such as is customary with the majority of adhesivetapes, and which gives the adhesive tape internal strength and ispermanently and fixedly connected to the pressure sensitive adhesive, isnot mandatory in the adhesive tape.

[0101] The adhesive tape of the invention is described below in apreferred embodiment, exemplified by a number of examples, withoutwishing thereby to restrict the invention in any way whatsoever. Alsogiven are comparative examples, which illustrate unsuitable adhesivetapes.

[0102] The following test methods are used to give a briefcharacterization of the specimens produced by the process described:

[0103] The bond strength is determined in accordance with BDF JOPMA002.In this method, an unbacked pressure sensitive adhesive film isinitially bonded to a 26 μm polyester film. The pressure sensitiveadhesive film/polyester film assembly is then applied to the substrate(steel) and subsequently peeled off under defined conditions using atensile testing machine. The peel angle is in each case 180°, the peelrate 300 mm/min. The force required for peel removal is the bondstrength.

[0104] The tack (surface tackiness) is measured by the rolling ballmethod in accordance with BDF test specification JOPM 0075.

[0105]  The measurement apparatus consists, accordingly, essentially ofan inclined plane, a steel ball, and a defined stainless steelsubstrate. The steel ball of 5.6 g (11 mm in diameter) rolls down theinclined plane (height 65 mm) at an angle of 21.50 onto the pressuresensitive adhesive and is braked by said adhesive by virtue of itspressure sensitive adhesion. The distance traveled by the ball on thesurface of the adhesive is taken as a measure of the tack. Accordingly,the tack is inversely proportional to the distance traveled.

[0106] The pH is determined by applying pH paper, wetted with distilledwater, to the surface of the adhesive, following an exposure time of 10minutes.

[0107] The volume resistance in the z direction, i.e., in the directionof the thickness of the pressure sensitive adhesive film, is measured inaccordance with ASTM-D-2739 with a weight load of 4 kg.

[0108] The coating of the pressure sensitive adhesive onto theantiadhesive medium (as a general rule, siliconized release paper) takesplace using a commercial coating machine from BASF or, in the case ofhotmelt pressure sensitive adhesives, with an extruder from Werner &Pfleiderer at temperatures from 170° C. to 200° C. using a slot die. Ineach case, specimens of the individual pressure sensitive adhesivesmeasuring 25×30 cm are produced. The thickness of the adhesive films canbe chosen freely and is set at between 0.04 mm and 0.8 mm.

[0109] Preparation of the natural rubber-based and EVA-based pressuresensitive adhesives and of the hotmelt pressure sensitive adhesivestakes place in commercial compounders from Stephan or AMK.

[0110] The acrylate-based pressure sensitive adhesives are produced in astirred tank reactor from Juchheim.

[0111] The A components of the solvent-free polyurethane pressuresensitive adhesives are prepared in a commercial dissolver from Molteni.Mixing with the B component (the isocyanate) immediately prior tocoating takes place using a two-component mixing and metering unit fromSpritztechnik-EMC.

[0112] The polyurethane-based pressure sensitive adhesives are preparedsolventlessly in a two-component reactive process. For this purpose, inthe examples, the A component in each case is first prepared by mixingthe corresponding starting materials in a commercial evacuatabledissolver from Molteni. In order to ensure no bubbles are present, thisis done with application of vacuum. The mixing time is in each caseapproximately 2 hours.

[0113] Mixing with the B component (the isocyanate) immediately prior tocoating takes place using a two-component mixing and metering unit fromSpritztechnik-EMC. The mixing system is dynamic. The mixing head isdesigned for two liquid components. The mixing rotor has a variablespeed of up to max. approx. 5 000 rpm. The metering pumps of this unitare gear pumps with a capacity of max. approx. 2 l/min.

[0114] The mixture is applied to siliconized release paper.

[0115] The chemical reaction of the two mixed components to give thepressure sensitive adhesive takes place at 70° C. in a drying oven.

EXAMPLES

[0116] The adhesive tape of the invention is described on the basis offive exemplary, known pressure sensitive adhesives (PSAs) differing intheir polymer and/or raw material basis, which are described below.These formulas form the basis for the individual examples 1 to 25, inwhich the adhesive tape of the invention is described, and for thecomparative examples.

[0117] Known PSA 1:

[0118] (Based on Acrylate Copolymer)

[0119] A 2 l reactor conventional for radical polymerizations is chargedwith

[0120] 20 g of hydroxypropyl acrylate

[0121] 60 g of methyl acrylate

[0122] 210 g of ethylhexyl acrylate

[0123] 210 g of butyl acrylate

[0124] 300 g of acetone/special boiling point spirit 60/95 (1:1).

[0125] Nitrogen gas is passed through the reactor with stirring for 45minutes and then the reactor is heated to 58° C. and 0.2 g ofazoisobutyronitrile (AIBN) is added. Thereafter, the external heatingbath is heated to 75° C. and the reaction is carried out constantly atthis temperature.

[0126] After a reaction time of 1 hour a further 0.2 g of AIBN is added.

[0127] After 2.5 hours and 5 hours, in each case 150 g ofacetone/special boiling point spirit 60/95 (1:1) are added for dilution.

[0128] The reaction is terminated after a time of 48 hours and theproduct is cooled to room temperature.

[0129] Following the addition of the alkaline filler and of the metalpowder (see the individual examples), 2.5 g of Desmodur Z® are added,based on the above proportions.

[0130] Known PSA 2:

[0131] (Based on Natural Rubber)

[0132] A PSA prepared in a compounder by conventional methods is used,with the following composition: Weight fraction Manufacturer/ (% by wt.)Trade name Chemical basis Supplier 46.0 Natural rubber SMR Naturalrubber Weber & Schaer CV50 ® 26.0 Zonarez B 115 S ® Poly-beta-pineneArizona resin 10.0 Dertophene T 110 ® Terpene-phenolic DRT resin 7.0Resin 731 D ® Rosin Abieta 7.0 Nipol 1312 LV ® Acrylonitrile- Zeonbutadiene copolymer 3.0 Zinc oxide Zinc oxide Grillo Weiβsiegel ® 1.0Irganox 1010 ® Sterically Ciba-Geigy hindered phenol

[0133] The PSA is prepared and used at a concentration of 20% inpetroleum spirit/ethanol (100:5).

[0134] Known PSA 3:

[0135] (Based on Styrene Block Copolymer)

[0136] A PSA prepared in a compounder by conventional methods is used insolvent-free form, with the following composition: Weight fractionManufacturer/ (% by wt.) Trade name Chemical basis Supplier 45.0 Vector4113 ® Styrene-isoprene- Exxon Mobil styrene block copolymer 45.0Escorez 2203 ® Aromatic-modified Exxon Mobil C-5 hydrocarbon resin 9.0Ondina G41 ® White oil Shell Chemicals 1.0 Irganox 1010 ® Stericallyhindered Ciba-Geigy phenol

[0137] Known PSA 4:

[0138] (Based on EVA)

[0139] A PSA prepared in a compounder by conventional methods, is usedat a concentration of 30% in toluene, with the following composition:Weight fraction Manufacturer/ (% by wt.) Trade name Chemical basisSupplier 70.0 Levapren 456 ® Polyethylene-vinyl Bayer acetate with avinyl acetate content of 45% 30.0 Foral 85 ® Hydrogenated rosinHercules/Eastman ester

[0140] Known PSA 5:

[0141] (Based on Polyurethane)

[0142] The following raw materials form the A component of thetwo-component PSA and are mixed solventlessly by known methods in adissolver for 2 hours, with application of vacuum for devolatilization.A Component: Weight fraction Manufacturer/ (% by wt.) Trade nameChemical basis Supplier 6.4 Arcol 1004 ® Polypropylene glycol, Bayerdiol 88.5 Baycoll BT 5031 ® Polypropylene glycol, Bayer triol 4.8Aerosil R202 ® Hydrophobicized Degussa pyrogenic silica 0.3 Mark DBTL ®Dibutyltin dilaurate Nordmann, Rassmann

[0143] The B component is isophorone diisocyanate (trade name: VestanatIPDI, manufacturer: Hüls). 7.8 parts of IPDI are required per 100 partsof the above A component. The NCO/OH ratio is then 0.95. The B componentis not added until after the alkaline filler and the metal powder (seeindividual examples) have been added, immediately prior to coating,using a two-component mixing and metering unit.

[0144] For the description of the adhesive tape of the invention, in theexamples the following alkaline fillers are used: TABLE 1 Alkalinefillers used in the examples Diameter of Chemical basis/ Manufacturer/at least 80% Trade name description Supplier of the particlesWeiβfeinkalk ® Calcium oxide RWK <0.1 mm powder Sodium carbonate Sodiumcarbonate Aldrich <0.5 mm powder powder Sodium carbonate Sodiumcarbonate Aldrich >0.5 mm granules granules Potassium Potassium Aldrich<0.5 mm carbonate powder carbonate powder

[0145] For the description of the adhesive tape of the invention,additionally, in the examples the following metal powders are used:TABLE 2 Metal powders used in the examples Diameter of Manufacturer/ atleast 80% Trade name Metal/description Supplier of the particles ECKAcopper Dendritic copper Eckart <0.16 mm CH-S 24 ® powder ECKA copperDendritic copper Eckart <0.045 mm CH-S No. 34862/ powder with G AG 5 ®silver coating STANDART Aluminum Eckart <0.125 mm aluminum powder powderin leaf Lack NOT ® form CONDUKT-O-FIL Silver-coated Potters- <0.05 mmS-3000-S3M ® glass beads Ballotini

Example 1

[0146] The PSA of the adhesive tape of the invention has the followingcomposition:

[0147] 65% by weight solids of the known PSA 1

[0148] 15% by weight sodium carbonate powder

[0149] 20% by weight ECKA copper CH-S 24®

[0150] For its preparation, 115 g of sodium carbonate powder and 154 gof ECKA copper CH-S 24® are added to 1 100 g of the cooled solution ofthe known PSA 1 (corresponding to 500 g of solids). Following theaddition of Desmodur Z®, the mixture is stirred for 1 hour.

[0151] The PSA is then applied from solution to a siliconized releasepaper, and drying and crosslinking take place in a drying oven initiallyat 60° C. and after 10 minutes at 120° C.

[0152] The thickness of the PSA film is set at

[0153] a) 0.06 mm and at

[0154] b) 0.1 mm.

[0155] The bond strength of the PSA film is

[0156] a) 1.3 N/cm,

[0157] b) 1.6 N/cm.

[0158] The rolling ball tack figures are:

[0159] a) 25 mm,

[0160] b) 18 mm.

[0161] The pH is in each case from 9.0 to 9.5.

[0162] The volume resistance in the z direction is:

[0163] a) 0.5 Ωm,

[0164] b) 3.1 Ωm.

[0165] After a storage time of one year the figures are unchanged.

Example 2

[0166] The PSA of the adhesive tape of the invention has the followingcomposition:

[0167] 65% by weight solids of the known PSA 1

[0168] 15% by weight Weiβfeinkalk®

[0169] 20% by weight ECKA copper CH-S 24®

[0170] For its preparation, 115 g of Weiβfeinkalk® and 154 g of ECKAcopper CH-S 24® are added to 1 100 g of the cooled solution of the knownPSA 1 (corresponding to 500 g of solids). Following the addition ofDesmodur Z®, the mixture is stirred for 1 hour.

[0171] The PSA is then applied from solution to a siliconized releasepaper, and drying and crosslinking take place in a drying oven initiallyat 60° C. and after 10 minutes at 120° C.

[0172] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0173] The bond strength of the PSA film is a) 1.1 N/cm and b) 1.3 N/cm.

[0174] The rolling ball tack figures are a) 39 mm and b) 25 mm.

[0175] The pH is in each case from 10.0 to 10.5.

[0176] The volume resistance in the z direction is a) 0.4 Ωm and b) 2.4Ωm.

[0177] After a storage time of one year the figures are unchanged.

Example 3

[0178] The PSA of the adhesive tape of the invention has the followingcomposition:

[0179] 65% by weight solids of the known PSA 1

[0180] 15% by weight of Weiβfeinkalk®

[0181] 20% by weight of CONDUKT-O-FIL S-3000-S3M®

[0182] For its preparation, 115 g of Weiβfeinkalk® and 154 g ofCONDUKT-O-FIL S-3000-S3M® are added to 1 100 g of the cooled solution ofthe known PSA 1 (corresponding to 500 g of solids). Following theaddition of Desmodur Z®, the mixture is stirred for 1 hour. The PSA isthen applied from solution to a siliconized release paper, and dryingand crosslinking take place in a drying oven initially at 60° C. andafter 10 minutes at 120° C.

[0183] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0184] The bond strength of the PSA film is a) 0.9 N/cm and b) 1.2 N/cm.

[0185] The rolling ball tack figures are a) 33 mm and b) 26 mm.

[0186] The pH is in each case from 9.5 to 10.0.

[0187] The volume resistance in the z direction is a) 1.4 Ωm and b) 27.1Ωm.

[0188] After a storage time of one year the figures are unchanged.

Example 4

[0189] The PSA of the adhesive tape of the invention has the followingcomposition:

[0190] 65% by weight solids of the known PSA 2

[0191] 15% by weight sodium carbonate powder

[0192] 20% by weight ECKA copper CH-S 24®

[0193] For its preparation, 15 g of sodium carbonate powder and 20 g ofECKA copper CH-S 24® are added to 325 g of the known PSA 2 present in20% strength petroleum spirit/ethanol solution (corresponding to 65 g ofsolids).

[0194] After a kneading time of 1 hour, the PSA is applied from solutionto a siliconized release film and is dried in a drying oven first at 60°C. and after 10 minutes at 110° C.

[0195] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0196] The bond strength of the PSA film is a) 1.4 N/cm and b) 1.8 N/cm.

[0197] The rolling ball tack figures are a) 20 mm and b) 15 mm.

[0198] The pH is in each case from 8.5 to 9.0.

[0199] The volume resistance in the z direction is a) 0.7 Ωm and b) 1.4Ωm.

[0200] After a storage time of one year the figures are unchanged.

Example 5

[0201] The PSA of the adhesive tape of the invention has the followingcomposition:

[0202] 65% by weight solids of the known PSA 2

[0203] 15% by weight sodium carbonate/potassium carbonate powder (mixingratio 1:1)

[0204] 20% by weight ECKA copper CH-S 24®

[0205] For its preparation, 15 g of sodium carbonate/potassium carbonatepowder (mixing ratio 1:1) and 20 g of ECKA copper CH-S 24® are added to325 g of the known PSA 2 present in 20% strength petroleumspirit/ethanol solution (corresponding to 65 g of solids).

[0206] After a kneading time of 1 hour, the PSA is applied from solutionto a siliconized release film and is dried in a drying oven first at 60°C. and after 10 minutes at 110° C.

[0207] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0208] The bond strength of the PSA film is a) 1.3 N/cm and b) 1.6 N/cm.

[0209] The rolling ball tack figures are a) 18 mm and b) 13 mm.

[0210] The pH is in each case from 8.5 to 9.0.

[0211] The volume resistance in the z direction is a) 0.6 Ωm and b) 1.3Ωm.

[0212] After a storage time of one year the figures are unchanged.

Example 6

[0213] The PSA of the adhesive tape of the invention has the followingcomposition:

[0214] 65% by weight solids of the known PSA 2

[0215] 15% by weight Weiβfeinkalk®

[0216] 20% by weight ECKA copper CH-S No. 34862/G AG 5®

[0217] For its preparation, 15 g of Weiβfeinkalk® and 20 g of ECKAcopper CH-S No. 34862/G AG 5® are added to 325 g of the known PSA 2present in 20% strength petroleum spirit/ethanol solution (correspondingto 65 g of solids).

[0218] After a kneading time of 1 hour, the PSA is applied from solutionto a siliconized release film and is dried in a drying oven first at 60°C. and after 10 minutes at 110° C.

[0219] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0220] The bond strength of the PSA film is a) 1.4 N/cm and b) 1.7 N/cm.

[0221] The rolling ball tack figures are a) 20 mm and b) 16 mm.

[0222] The pH is in each case from 9.5 to 10.0.

[0223] The volume resistance in the z direction is a) 2.4 Ωm and b) 36.1Ωm.

[0224] After a storage time of one year the figures are unchanged.

Example 7

[0225] The PSA of the adhesive tape of the invention has the followingcomposition:

[0226] 65% by weight known PSA 3

[0227] 15% by weight Weiβfeinkalk®

[0228] 20% by weight ECKA copper CH-S 24®

[0229] For its preparation, 750 g of Weiβfeinkalk® and 1 000 g of ECKAcopper CH-S 24® are added to 3 250 g of the known PSA 3.

[0230] After a kneading time of 1 hour, the PSA is applied by theextrusion process to a siliconized release film.

[0231] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0232] The bond strength of the PSA film is a) 2.2 N/cm and b) 2.9 N/cm.

[0233] The rolling ball tack figures are a) 18 mm and b) 7 mm.

[0234] The pH is in each case from 9.5 to 10.0.

[0235] The volume resistance in the z direction is a) 0.5 Ωm and b) 1.3Ωm.

[0236] After a storage time of one year the figures are unchanged.

Example 8

[0237] The PSA of the adhesive tape of the invention has the followingcomposition:

[0238] 65% by weight known PSA 3

[0239] 15% by weight Weiβfeinkalk®

[0240] 20% by weight ECKA copper CH-S No. 34862/G AG 5®

[0241] For its preparation, 750 g of Weiβfeinkalk® and 1 000 g of ECKAcopper CH-S No. 34862/G AG 5® are added to 3 250 g of the known PSA 3.

[0242] After a kneading time of 1 hour, the PSA is applied by theextrusion process to a siliconized release film.

[0243] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0244] The bond strength of the PSA film is a) 2.4 N/cm and b) 2.8 N/cm.

[0245] The rolling ball tack figures are a) 16 mm and b) 9 mm.

[0246] The pH is in each case from 9.5 to 10.0.

[0247] The volume resistance in the z direction is a) 1.8 Ωm and b) 20.4Ωm.

[0248] After a storage time of one year the figures are unchanged.

Example 9

[0249] The PSA of the adhesive tape of the invention has the followingcomposition:

[0250] 65% by weight known PSA 3

[0251] 15% by weight Weiβfeinkalk®

[0252] 20% by weight STANDART aluminum powder Lack NOT®

[0253] For its preparation, 750 g of Weiβfeinkalk® and 1 000 g ofSTANDART aluminum powder Lack NOT® are added to 3 250 g of the known PSA3.

[0254] After a kneading time of 1 hour, the PSA is applied by theextrusion process to a siliconized release film.

[0255] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0256] The bond strength of the PSA film is a) 1.7 N/cm and b) 1.9 N/cm.

[0257] The rolling ball tack figures are a) 25 mm and b) 17 mm.

[0258] The pH is in each case from 9.5 to 10.0.

[0259] The volume resistance in the z direction is a) 85.6 Ωm and b)130.3 Ωm.

[0260] After a storage time of one year the figures are unchanged.

Example 10

[0261] The PSA of the adhesive tape of the invention has the followingcomposition:

[0262] 65% by weight solids of the known PSA 4

[0263] 15% by weight Weiβfeinkalk®

[0264] 20% by weight ECKA copper CH-S 24®

[0265] For its preparation, 21 g of Weiβfeinkalk® and 28 g of ECKAcopper CH-S 24® are added to 300 g of the known PSA 4 present at aconcentration of 30% in toluene (corresponding to 90 g of solids).

[0266] After a kneading time of 1 hour, the PSA is applied from solutionto a siliconized release paper and is dried in a drying oven first at60° C. and after 10 minutes at 130° C.

[0267] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0268] The bond strength of the PSA film is a) 0.8 N/cm and b) 1.1 N/cm.

[0269] The rolling ball tack figures are a) 33 mm and b) 28 mm.

[0270] The pH is in each case from 9.5 to 10.0.

[0271] The volume resistance in the z direction is a) 0.3 Ωm and b) 4.9Ωm.

[0272] After a storage time of one year the figures are unchanged.

Example 11

[0273] The PSA of the adhesive tape of the invention has the followingcomposition:

[0274] 65% by weight solids of the known PSA 4

[0275] 15% by weight Weiβfeinkalk®

[0276] 20% by weight CONDUKT-O-FIL S-3000-S3M®

[0277] For its preparation, 21 g of Weiβfeinkalk® and 28 g ofCONDUKT-O-FIL S-3000-S3M® are added to 300 g of the known PSA 4 presentat a concentration of 30% in toluene (corresponding to 90 g of solids).

[0278] After a kneading time of 1 hour, the PSA is applied from solutionto a siliconized release paper and is dried in a drying oven first at60° C. and after 10 minutes at 130° C.

[0279] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0280] The bond strength of the PSA film is a) 0.7 N/cm and b) 0.9 N/cm.

[0281] The rolling ball tack figures are a) 40 mm and b) 31 mm.

[0282] The pH is in each case from 9.5 to 10.0.

[0283] The volume resistance in the z direction is a) 1.9 Ωm and b) 33.2Ωm.

[0284] After a storage time of one year the figures are unchanged.

Example 12

[0285] The PSA of the adhesive tape of the invention has the followingcomposition:

[0286] 35% by weight solids of the known PSA 5

[0287] 5% by weight Weiβfeinkalk®

[0288] 60% by weight ECKA copper CH-S 24®

[0289] For its preparation, 46.2 g of Weiβfeinkalk® and, in portions,554.4 g of ECKA copper CH-S 24® are added to 300 g of the A component ofthe known PSA 5.

[0290] After a mixing time of 2 hours in the dissolver under vacuum,23.4 g of Vestanat IPDI® (B component) are admixed using a 2-componentmixing and metering unit and the mixture is applied to a siliconizedrelease paper.

[0291] The chemical reaction of the two mixed components to give the PSAtakes place at 70° C. in a drying oven.

[0292] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0293] The bond strength of the PSA film is a) 0.1 N/cm and b) 0.1 N/cm.

[0294] The rolling ball tack figures are a) 95 mm and b) 90 mm.

[0295] The pH is in each case from 8.5.

[0296] The volume resistance in the z direction is a) 0.06 Ωm and b)0.09 Ωm.

[0297] After a storage time of one year the figures are unchanged.

Example 13

[0298] The PSA of the adhesive tape of the invention has the followingcomposition:

[0299] 65% by weight solids of the known PSA 5

[0300] 15% by weight Weiβfeinkalk®

[0301] 20% by weight ECKA copper CH-S 24®

[0302] For its preparation, 74.6 g of Weiβfeinkalk® and 99.5 g of ECKAcopper CH-S 24® are added to 300 g of the A component of the known PSA5.

[0303] After a mixing time of 2 hours in the dissolver under vacuum,23.4 g of Vestanat IPDI® (B component) are admixed using a 2-componentmixing and metering unit and the mixture is applied to a siliconizedrelease paper.

[0304] The chemical reaction of the two mixed components to give the PSAtakes place at 70° C. in a drying oven.

[0305] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0306] The bond strength of the PSA film is a) 1.4 N/cm and b) 1.8 N/cm.

[0307] The rolling ball tack figures are a) 16 mm and b) 9 mm.

[0308] The pH is in each case from 9.5 to 10.0.

[0309] The volume resistance in the z direction is a) 0.3 Ωm and b) 0.9Ωm.

[0310] After a storage time of one year the figures are unchanged.

Example 14

[0311] The PSA of the adhesive tape of the invention has the followingcomposition:

[0312] 55% by weight of the known PSA 5

[0313] 40% by weight Weiβfeinkalk®

[0314] 5% by weight ECKA copper CH-S 24®

[0315] For its preparation, 235.2 g of Weiβfeinkalk® and, in portions,29.4 g of ECKA copper CH-S 24® are added to 300 g of the A component ofthe known PSA 5.

[0316] After a mixing time of 2 hours in the dissolver under vacuum,23.4 g of Vestanat IPDI® (B component) are admixed using a 2-componentmixing and metering unit and the mixture is applied to a siliconizedrelease paper.

[0317] The chemical reaction of the two mixed components to give the PSAtakes place at 70° C. in a drying oven.

[0318] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0319] The bond strength of the PSA film is a) 0.1 N/cm and b) 0.2 N/cm.

[0320] The rolling ball tack figures are a) 88 mm and b) 69 mm.

[0321] The pH is in each case 12.0.

[0322] The volume resistance in the z direction is a) 160 Ωm and b) 420Ωm.

[0323] After a storage time of one year the figures are unchanged.

Example 15

[0324] The PSA of the adhesive tape of the invention has the followingcomposition:

[0325] 65% by weight of the known PSA 5

[0326] 15% by weight Weiβfeinkalk®

[0327] 20% by weight ECKA copper CH-S No. 34862/G AG 5®

[0328] For its preparation, 74.6 g of Weiβfeinkalk® and 99.5 g of ECKAcopper CH-S No. 34862/G AG 5® are added to 300 g of the A component ofthe known PSA 5.

[0329] After a mixing time of 2 hours in the dissolver under vacuum,23.4 g of Vestanat IPDI® (B component) are admixed using a 2-componentmixing and metering unit and the mixture is applied to a siliconizedrelease paper.

[0330] The chemical reaction of the two mixed components to give the PSAtakes place at 70° C. in a drying oven.

[0331] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0332] The bond strength of the PSA film is a) 1.3 N/cm and b) 1.7 N/cm.

[0333] The rolling ball tack figures are a) 17 mm and b) 9 mm.

[0334] The pH is in each case from 9.5 to 10.0.

[0335] The volume resistance in the z direction is a) 7.3 Ωm and b) 44.1Ωm.

[0336] After a storage time of one year the figures are unchanged.

[0337] Examples 16 to 25

[0338] Table 3 lists the base materials used to prepare apolyurethane-based PSA film, in each case with their trade name andmanufacturer. The chemicals named are all freely available commercially.TABLE 3 Base materials used to prepare the polyurethane-based PSA film,with trade name and manufacturer Trade name Chemical basisManufacturer/Supplier Arcol 1004 ® Polypropylene glycol, Bayer diol (M =430) Arcol P 1000 N ® Polypropylene glycol, Bayer diol (M = 1 000) Arcol1067S ® Polypropylene glycol, Bayer triol (M = 1 000) Baycoll BT 5031 ®Polypropylene glycol, Bayer triol (M = 6 200) Mark DBTL ® Dibutyltindilaurate Nordmann, Rassmann Vestanat IPDI ® Isophorone diisocyanateHüls Aerosil R202 ® Hydrophobicized pyrogenic Degussa silica

[0339] For the description of the polyurethane-based adhesive tape ofthe invention, in the following examples the alkaline fillers and metalpowders as shown in tables 1 and 2 are used.

Example 16

[0340] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol 1004 ® 2.0 Baycoll BT 5031 ® 27.4 ECKA copperCH-S 24 ® 60.0 Weissfeinkalk ® 5.0 Aerosil R 202 ® 3.0 Mark DBTL ® 0.2B-component Vestanat IPDI ® 2.4

[0341] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0342] The bond strength of the PSA film is a) 0.1 N/cm and b) 0.1 N/cm.

[0343] The rolling ball tack figures are a) 95 mm and b) 90 mm.

[0344] The pH is in each case 8.5.

[0345] The volume resistance in the z direction is a) 0.06 Ωm and b)0.09 Ωm.

[0346] After a storage time of one year the figures are unchanged.

[0347] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 17

[0348] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol 1004 ® 3.8 Baycoll BT 5031 ® 53.3 ECKA copperCH-S 24 ® 20.0 Weissfeinkalk ® 15.0 Aerosil R 202 ® 3.0 Mark DBTL ® 0.2B-component Vestanat IPDI ® 4.7

[0349] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0350] The bond strength of the PSA film is a) 1.4 N/cm and b) 1.8 N/cm.

[0351] The rolling ball tack figures are a) 16 mm and b) 9 mm.

[0352] The pH is in each case from 9.5 to 10.

[0353] The volume resistance in the z direction is a) 0.3 Ωm and b) 0.9Ωm.

[0354] After a storage time of one year the figures are unchanged.

[0355] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 18

[0356] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol 1004 ® 3.2 Baycoll BT 5031 ® 44.6 ECKA copperCH-S 24 ® 5.0 Weissfeinkalk ® 40.0 Aerosil R 202 ® 3.0 Mark DBTL ® 0.2B-component Vestanat IPDI ® 4.0

[0357] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0358] The bond strength of the PSA film is a) 0.1 N/cm and b) 0.2 N/cm.

[0359] The rolling ball tack figures are a) 88 mm and b) 69 mm.

[0360] The pH is in each case 12.

[0361] The volume resistance in the z direction is a) 160 Ωm and b) 420Ωm.

[0362] After a storage time of one year the figures are unchanged.

[0363] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 19

[0364] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol 1004 ® 3.8 Baycoll BT 5031 ® 53.3 ECKA copperCH-S No. 34862/G 20.0 AG 5 ® Weissfeinkalk ® 15.0 Aerosil R 202 ® 3.0Mark DBTL ® 0.2 B-component Vestanat IPDI ® 4.7

[0365] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0366] The bond strength of the PSA film is a) 1.3 N/cm and b) 1.7 N/cm.

[0367] The rolling ball tack figures are a) 17 mm and b) 9 mm.

[0368] The pH is in each case from 9.5 to 10.

[0369] The volume resistance in the z direction is a) 7.3 Ωm and b) 44.1Ωm.

[0370] After a storage time of one year the figures are unchanged.

[0371] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 20

[0372] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol 1004 ® 3.8 Baycoll BT 5031 ® 53.3CONDUKT-O-FIL S-3000-S3M ® 20.0 Weissfeinkalk ® 15.0 Aerosil R 202 ® 3.0Mark DBTL ® 0.2 B-component Vestanat IPDI ® 4.7

[0373] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0374] The bond strength of the PSA film is a) 0.8 N/cm and b) 0.9 N/cm.

[0375] The rolling ball tack figures are a) 33 mm and b) 47 mm.

[0376] The pH is in each case from 9.5 to 10.

[0377] The volume resistance in the z direction is a) 17 Ωm and b) 133Ωm.

[0378] After a storage time of one year the figures are unchanged.

[0379] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 21

[0380] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol 1004 ® 3.8 Baycoll BT 5031 ® 53.3 STANDARTAluminum Powder Lack 20.0 NOT ® Weissfeinkalk ® 15.0 Aerosil R 202 ® 3.0Mark DBTL ® 0.2 B-component Vestanat IPDI ® 4.7

[0381] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0382] The bond strength of the PSA film is a) 0.6 N/cm and b) 0.8 N/cm.

[0383] The rolling ball tack figures are a) 64 mm and b) 68 mm.

[0384] The pH is in each case from 9.0 to 9.5.

[0385] The volume resistance in the z direction is a) 23 Ωm and b) 130Ωm.

[0386] After a storage time of one year the figures are unchanged.

[0387] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 22

[0388] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol P 1000 N ® 34.5 Arcol 1067 S ® 15.4 ECKAcopper CH-S 24 ® 20.0 Weissfeinkalk ® 15.0 Aerosil R 202 ® 3.0 MarkDBTL ® 0.2 B-component Vestanat IPDI ® 11.9

[0389] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0390] The bond strength of the PSA film is a) 2.4 N/cm and b) 2.7 N/cm.

[0391] The rolling ball tack figures are a) 12 mm and b) 9 mm.

[0392] The pH is in each case from 9.0 to 9.5.

[0393] The volume resistance in the z direction is a) 0.8 Ωm and b) 1.8Ωm.

[0394] After a storage time of one year the figures are unchanged.

[0395] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 23

[0396] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol P 1000 N ® 34.5 Arcol 1067 S ® 15.4 ECKAcopper CH-S 24 ® 20.0 Sodium carbonate powder 15.0 Aerosil R 202 ® 3.0Mark DBTL ® 0.2 B-component Vestanat IPDI ® 11.9

[0397] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0398] The bond strength of the PSA film is a) 1.9 N/cm and b) 2.3 N/cm.

[0399] The rolling ball tack figures are a) 12 mm and b) 9 mm.

[0400] The pH is in each case from 8.5 to 9.0.

[0401] The volume resistance in the z direction is a) 0.9 Ωm and b) 1.8Ωm.

[0402] After a storage time of one year the figures are unchanged.

[0403] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 24

[0404] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol P 1000 N ® 34.5 Arcol 1067 S ® 15.4 ECKAcopper CH-S 24 ® 20.0 Potassium carbonate powder 15.0 Aerosil R 202 ®3.0 Mark DBTL ® 0.2 B-component Vestanat IPDI ® 11.9

[0405] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0406] The bond strength of the PSA film is a) 2.1 N/cm and b) 2.4 N/cm.

[0407] The rolling ball tack figures are a) 14 mm and b) 12 mm.

[0408] The pH is in each case from 9.0 to 9.5.

[0409] The volume resistance in the z direction is a) 1.3 Ωm and b) 12.4Ωm.

[0410] After a storage time of one year the figures are unchanged.

[0411] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

Example 25

[0412] The composition of the PSA of the polyurethane-based adhesivetape of the invention is as follows: Weight fraction Raw material [% byweight] A-component Arcol P 1000 N ® 34.5 Arcol 1067 S ® 15.4 ECKAcopper CH-S 24 ® 20.0 Sodium carbonate/potassium 15.0 carbonate powder(1:1) Aerosil R 202 ® 3.0 Mark DBTL ® 0.2 B-component Vestanat IPDI ®11.9

[0413] The thickness of the PSA film is set at a) 0.06 mm and at b) 0.1mm.

[0414] The bond strength of the PSA film is a) 2.0 N/cm and b) 2.3 N/cm.

[0415] The rolling ball tack figures are a) 12 mm and b) 11 mm.

[0416] The pH is in each case from 9.0 to 9.5.

[0417] The volume resistance in the z direction is a) 0.8 Ωm and b) 14.6Ωm.

[0418] After a storage time of one year the figures are unchanged.

[0419] Following repeated application of road earth to the PSA film andsubsequent removal by rinsing with mains water, the figures are likewiseunchanged.

COMPARATIVE EXAMPLES Comparative Example 1

[0420] In analogy to example 13, 15% by weight of sodium carbonategranules are used instead of 15% by weight of Weiβfeinkalk®.

[0421] A highly granular, inhomogeneous adhesive tape is obtained whosesurface possesses sharply delimited alkaline and nonalkaline regions inaccordance with the particle distribution of the sodium carbonate. Thealkalinity is not homogeneous.

Comparative Example 2

[0422] In analogy to example 15, the thickness of the PSA film is set at0.5 mm.

[0423] The adhesive tape is not electrically conductive. The volumeresistance in the z direction is 1.3×10⁸ Ωm.

Comparative Example 3

[0424] In analogy to example 23, 15% by weight of sodium carbonategranules are used instead of 15% by weight of sodium carbonate powder.

[0425] A highly granular, inhomogeneous adhesive tape is obtained whosesurface possesses sharply delimited alkaline and nonalkaline regions inaccordance with the particle distribution of the sodium carbonate. Thealkalinity is not homogeneous.

Comparative Example 4

[0426] In analogy to example 19, the thickness of the PSA film is set at0.5 mm.

[0427] The adhesive tape is not electrically conductive. The volumeresistance in the z direction is 1.3×10⁸ Ωm.

What is claimed is:
 1. A preferably unbacked adhesive tape withpermanent full-area pressure sensitive adhesion, composed of a film of apressure sensitive adhesive which is preferably coated onto anantiadhesive medium and comprises an alkaline, solid, pulverized,mineral filler with a weight fraction of between more than 0% by weightand 60% by weight, based on the total weight of the adhesive, so thatthe permanently pressure sensitively adhesive surface of the adhesivetape has a pH of more than 8, and a conductive additive, especially ametal powder, a powder coated with a metal, and/or metallized beads,with a weight fraction of between more than 0% by weight and 60% byweight, so that the adhesive tape is electrically conductive in the zdirection, i.e., in the direction of the thickness of the tape.
 2. Thetape as claimed in claim 1, wherein the particle diameter of the mineralfiller, based on at least 80% of said particles, is not more than 0.5mm, preferably not more than 0.1 mm.
 3. The tape as claimed in claim 1,wherein the particle diameter of the conductive additive, based on atleast 80% of said particles, is at least 30% of the thickness of thepressure sensitive adhesive film, preferably at least 70% of thethickness of said film.
 4. The tape as claimed in claim 1, wherein theweight fraction of the mineral filler is from 5% by weight to 40% byweight, preferably from 5% by weight to 30% by weight, with veryparticular preference from 5% by weight to 20% by weight, based on thetotal weight of the adhesive.
 5. The tape as claimed in claim 1, whereinthe weight fraction of the conductive additive is from 10% by weight to30% by weight, based on the total weight of the adhesive.
 6. The tape asclaimed in claim 1, wherein the bond strength of the pressure sensitiveadhesive film is at least 0.1 N/cm, preferably at least 0.01 N/cm,especially in the case of the polyurethane-based pressure sensitiveadhesive film.
 7. The tape as claimed in claim 1, wherein at least afigure of 100 mm or less is achieved in the rolling ball tack test,preferably at least a figure of 300 mm or less, especially in the caseof the polyurethane-based pressure sensitive adhesive film.
 8. The tapeas claimed in claim 1, wherein the pH of the surface of the pressuresensitive adhesive, especially when moistened, is at least 8.5 or more9. The tape as claimed in claim 1, wherein the volume resistance of thepressure sensitive adhesive film in the z direction is not more than 500Ωm, preferably at least not more than 1 000 Ωm, in particular in thecase of the polyurethane-based pressure sensitive adhesive film.
 10. Themethod of using a tape as claimed in claim 1 for application toelectrodes of electrostatic filters.